Oasis cold island effect and its influence on air temperature: a case study of Tarim Basin, Northwest China

Oasis effect can improve the regional climate and habitability of an arid region. In this study, we explored the cold island effects of oases distributed along the edge of Tarim Basin by analyzing the oasis cold island effect （OCIE） intensity, spatial-temporal variation of OCIE, factors influencing the OCIE and impacts of OCIE on air temperature using geographical statistics and GIS methods based on the MODIS land surface temperature, land use/cover change （LUCC） and observed air temperature data. Results showed that all the oases in the Tarim Basin exhibited cold island effects, with the OCIE intensity highest in summer （-9.08℃）, followed by autumn （-4.24℃） and spring （-3.85℃）. The total area of oasis cold island （OCI） and the comprehensive OCIE index showed the same seasonal change trend as the OCIE intensity. However, the changing trends in areas of OCI with strong, medium and weak OCIEs were inconsistent across different seasons. Farmland and water areas were found to be the key contributors that affected the OCIE, and the area and aggregation metrics of these two land use/cover types directly contributed to the OCIE. By contrast, natural vegetation, such as forest and grassland, almost had no contribution to the OCIE. Simulation of observed air temperature data showed that if farmland is replaced by forest or grassland in the oasis, the mean, maximum and minimum air temperatures will increase significantly. This heating effect will be higher in summer （reaching 1.14℃ to 2.08℃） and lower in spring and autumn. Moreover, the heating effect of farmland being replaced by forest will be higher than that of farmland being replaced by grassland. These results can provide a basis for understanding the cold island effect of oases in arid regions.

Change in Urban Wetlands and Their Cold Island Effects in Response to Rapid Urbanization

The cold-island effect of urban wetlands has received increasing attention in recent years due to its important role in the alleviation of urban heat islands.Hangzhou,a representative rapidly urbanizing city with rich wetlands in China,was selected as a case study for researching the changes that the urban wetlands have undergone and their impact on the urban thermal environment.Land surface temperature(LST) was acquired from the thermal infrared data of Landsat 5 Thematic Mapper(TM) images in 1990,1995,2000,2006,and 2010,using the single-channel method.The results are as follows:1) considering the changes in land use,the urban wetlands located to the west of Hangzhou have decreased significantly during 1990–2010 because of rapid urbanization.In the Xixi Wetland,the change in land use was relatively small and most of the water body and vegetation were preserved.However,to the east of the Xixi Wetland,large areas of water body and vegetation have been replaced by built-up land as a result of the urbanization process;2) considering the change in LST,it was found from land surface temperature retrieval that the changing spatial pattern of the thermal field was highly correlated with land use changes.Low temperature regions of the eastern Xixi Wetland were gradually eroded by high temperature regions,and the centroid of the heat island in East Xixi was found to be constantly shifting westward.In addition,the difference in LST between the Xixi Wetland and East Xixi has increased;3) considering the impact factors for this area,land use structure and patch shape were found to have a significant impact on LST,shown by the results of multiple linear stepwise regressions.Increasing the size of the wetlands in urban planning is considered to be the most effective measure in alleviating the urban heat island effect.Moreover,reducing the spatial complexity of landscape patches also contributes to the alleviation of the urban heat island effect.

Influence of the northern Yellow Sea Cold Water Mass on picoplankton distribution around the Zhangzi Island,northern Yellow Sea

Picoplankton distribution around the Zhangzi Island（northern Yellow Sea）was investigated by monthly observation from July 2009 to June 2010.Three picoplankton populations were discriminated by flow cytometry,namely Synechococcus,picoeukaryotes and heterotrophic prokaryotes.In summer（from July to September）,the edge of the northern Yellow Sea Cold Water Mass（NYSCWM）resulting from water column stratification was observed.In the NYSCWM,picoplankton（including Synechococcus,picoeukaryotes and heterotrophic prokaryotes）distributed synchronically with extremely high abundance in the thermocline（20 m）in July and August（especially in August）,whereas in the bottom zone of the NYSCWM（below 30 m）,picoplankton abundance was quite low.Synechococcus,picoeukaryotes and heterotrophic prokaryotes showed similar response to the NYSCWM,indicating they had similar regulating mechanism under the influence of NYSCWM.Whereas in the non-NYSCWM,Synechococcus,picoeukaryotes and heterotrophic prokaryotes exhibited different distribution patterns,suggesting they had different controlling mechanisms.Statistical analysis indicated that temperature,nutrients（NO3^and PO4^3-）and ciliate were important factors in regulating picoplankton distribution.The results in this study suggested that the physical event NYSCWM,had strong influence on picoplankton distribution around the Zhangzi Island in the northern Yellow Sea.

Tidal Effects on the Bottom Thermal Front of North Yellow Sea Cold Water Mass near Zhangzi Island in Summer 2009

Three seabed-mounted TD/CTD chains and two upward-looking acoustic Doppler current profilers (ADCPs) in the southwest of Zhangzi Island are used and a simultaneous cruise observation in the northern North Yellow Sea (NYS) is conducted to study temperature variation in the bottom thermal front zone of the NYS Cold Water Mass (NYSCWM) during the summer of 2009. In the flood-ebb tidal cycles, the bottom temperature decreases (increases) during flood (ebb) tides, which are dominated by the tidal-current induced horizontal advection. The ebb tide-induced temperature increase is larger than the flood tide-induced tempera- ture decrease due to seasonal warming. In the spring-neap tidal cycles, the temperature and the vertical temperature structure show notable fortnightly variation from 16 July to 25 August. The bottom temperature increases from neap to spring tides and decreases from spring to neap. The Richardson number demonstrates strengthened vertical mixing during spring tides but enhanced stratifica- tion during neap tides. The spring-neap variation in vertical shear caused by tidal current is the dominant factor that induces the fort- nightly variation in vertical mixing and thus bottom temperature.

白令海和阿留申群岛水文地理特征——《The Bering Sea and Aleutian Island:Region of Wonders》简评

由海事咨询计划顾问、阿拉斯加大学费尔班克斯分校渔业与海洋科学学院教授特里·约翰逊撰写的《The Bering Sea and Aleutian Island:Region of Wonders》一书于2003年由阿拉斯加海洋基金出版。该书一共分为八章,共191页,450多张彩色照片、地图等图件,88条参考文献,对白令海和阿留申群岛及其周边区域的水文地理特征进行了详细的描述。包括地理要素、自然环境、人文生态,以及资源能源等方面的内容。特里·约翰逊梳理了白令海和阿留申群岛区域水文地理探索的新成果,对中国寒区海域认识和研究具有重要的参考价值。

Monitoring Intra-annual Spatiotemporal Changes in Urban Heat Islands in 1449 Cities in China Based on Remote Sensing

This study aimed to accurately study the intra-annual spatiotemporal variation in the surface urban heat island intensities(SUHIIs) in 1449 cities in China.First, China was divided into five environmental regions.Then, the SUHIIs were accurately calculated based on the modified definitions of the city extents and their corresponding nearby rural areas.Finally, we explored the spatiotemporal variation of the mean, maximum, and minimum values, and ranges of SUHIIs from several aspects.The results showed that larger annual mean daytime SUHIIs occurred in hot-humid South China and cold-humid northeastern China, and the smallest occurred in arid and semiarid west China.The seasonal order of the SUHIIs was summer > spring > autumn > winter in all the temperate regions except west China.The SUHIIs were obviously larger during the rainy season than the dry season in the tropical region.Nevertheless, significant differences were not observed between the two seasons within the rainy or dry periods.During the daytime, the maximum SUHIIs mostly occurred in summer in each region, while the minimum occurred in winter.A few cold island phenomena existed during the nighttime.The maximum SUHIIs were generally significantly positively correlated with the minimum SUHIIs during the daytime, nighttime and all-day in all environmental regions throughout the year and the four seasons.Moreover, significant correlation scarcely existed between the daytime and nighttime ranges of the SUHIIs.In addition, the daytime SUHIIs were also insignificantly correlated with the nighttime SUHIIs in half of the cases.

核岛冷链通风空调系统性能优化研究

核岛冷链通风空调系统的设计存在余量值过大、运行能耗高、调节控制笨重等问题。为了降低核电的成本,本文基于“华龙一号”某厂房实际通风空调系统,建立了主要能耗设备的数学模型,确定了系统节能优化目标函数和约束条件,使用遗传算法研究了通风空调系统节能运行的优化效果。分别计算了2种优化方案在负荷率变化和高温与常温末端负荷比不同时,系统整体及各设备能耗情况。结果表明:单台冷水机组运行,高温与常温末端串联的系统形式节能率为14.1%,但随着末端负荷比的增大,节能率降低;单台冷水机组运行,高温与常温末端串联、高温末端额外增加高温冷水机组的系统形式在负荷比为2时节能率为17.2%,节能效果优于方案1的12.2%。

岛状多年冻土区高速铁路路基热状态及工程措施效果分析

为揭示岛状多年冻土区高速铁路路基热状态,提出合理有效的制冷结构,在新建哈尔滨至伊春高速铁路某车站试验段开展现场监测,获得岛状多年冻土的地温数据;基于实测地温数据,采用冻土水热耦合理论,对将在试验段实施的两侧双排普通热棒路基、两侧双排+中心单排全季热棒路基、两侧单排+基底横向通铺全季热棒路基3种制冷路基结构进行数值模拟,对比了3种制冷路基结构的地温分布特征及对下伏岛状多年冻土的降温效果。研究结果表明:铁力地区年均气温和降水呈增大趋势,天然场地岛状多年冻土地温在-0.3℃左右,属于高温极不稳定多年冻土。3种制冷路基结构中,两侧单排+基底横向通铺全季热棒对岛状多年冻土保护及降温效果最优,两侧双排普通热棒最差。普通热棒路基的多年冻土上限呈“两侧凸,中间凹”形态,抬升不明显;全季热棒路基的多年冻土上限呈“上凸缓斜平顶”形态,抬升显著。研究成果可对多年冻土区高速铁路路基建设和结构优化提供技术支撑。

城市公园冷岛效应研究进展综述

在城市快速发展的背景下,城市地表覆盖类型以及景观格局演变导致了一系列环境问题,气候变化和极端天气频繁发生,城市热岛现象已经成为最主要的环境问题之一,城市公园作为减缓城市热岛效应的重要手段已被广泛接受,目前针对城市热岛效应的基础研究较多,而对城市公园冷岛效应研究较少。文中采用知识图谱分析方法和文献计量分析,对年度发文量、机构、作者、关键词和研究进程进行分析,阐明了城市公园冷岛效应的研究现状、理清其发展趋势,旨在为未来城市公园冷岛效应研究提供借鉴与参考。

不同城市热岛梯度下公园冷岛效应和景观特征的关联机制

城市公园形成的冷岛效应已成为缓解城市热环境的重要途径之一。利用Landsat 8 OLI-TIRS、Google Earth遥感数据,通过辐射传导算法反演济南市22个公园的地表温度;采用缓冲区分析、多元统计和相关性分析等方法定量分析公园内部平均温度、公园冷岛效应与公园内部机理以及城市形态两大景观特征之间的关系;利用增长回归树模型初步探究景观特征的贡献能力。结果表明:1)不同城市热岛梯度下公园冷岛效应呈梯度变化,热岛等级高的公园,其冷岛效应更显著;2)当公园面积达到200 hm^(2)、水体面积达到45 hm^(2)、绿地面积在80~100 hm^(2)时,公园的冷岛效应最佳,水体比绿地的冷却效果更强;3)建筑高度与冷岛效应相关性最显著,当建筑高度在35~63 m时,最大冷却距离随高度的增大而增加,过高过密且杂乱无序的建筑环境阻碍公园冷岛效应;4)内在机理对公园地表温度、最大冷却距离、冷却强度的贡献能力强于外部城市形态指标,外部城市形态对冷却梯度的贡献能力更强。因此,在不同城市热岛梯度下,将公园绿地、水体面积控制在阈值内,适当增加公园轮廓复杂度和不透水面积,并利用城市风廊增加公园冷空气溢出途径,能够改善公园周围热环境、提高人体舒适度。

绿蓝空间协同作用下建筑街区的热湿环境分析

为分析绿蓝空间协同作用下环湖建筑街区的热湿环境,采用了CFD(计算流体力学)的方法对4种典型建筑街区形态进行了数值模拟。结果表明:气流作用下,绿蓝空间对中下游建筑街区的温湿度影响较大,尤其是两岸和下游中央区域。其中等高型(H=8 m)、环湖上升型由于建筑高度较低,气流更快地通过街区,形成“扩散状”温湿度分布;等高型(H=12 m)、环湖下降型由于低温气流在水体上空没有足够时间沉降,形成“聚集状”温湿度分布,从而在植被附近形成多个冷旋涡,进而产生局域的“冷岛效应”。蓝色空间取代部分密集建筑街区,在与绿色空间协同作用下,通过合理布局能较大幅度优化建筑街区环境。

寒潮背景下舟山群岛气温空间插值方案对比评估

在测站稀疏的海岛地区,如何科学选择插值方案以合理体现气象要素的空间分布特征是精细化监测面临的重要问题。以舟山群岛为例,挑选了有中尺度站观测以来(2014—2021年)影响舟山的8次寒潮过程,对比检验了普通克里格(Ordinary Kriging, OK)、反距离权重(Inverse Distance Weighing, IDW)、ANUSPLIN(以下简称ANU)三种方案的插值效果。针对8次过程的过程最低气温、日最低气温降幅和日平均气温降幅,在53个测站中随机选取11个检验站点,发现ANU的插值误差高于OK和IDW。进一步设计了周边站点密集、周边站点稀疏、检验站点脱离本岛三组插值试验,分析表明,ANU的插值表现与周边站点的密集程度息息相关:当周边站点密集时,ANU的插值误差小于OK和IDW;当周边站点稀疏时,ANU的插值误差明显高于OK和IDW。在周边站点密集分布的情形下,无论检验站点位于舟山本岛还是零散小岛上,ANU均能取得最优插值效果,说明在气温插值中ANU对地形的依赖相对较小,插值精度对插值效果的影响亦较小。

合肥市夏季城市公园降温效应与优化策略研究

随着我国城镇的快速化发展,城市热环境问题日益恶化。作为城市绿色空间的重要构成部分,城市公园在优化城市热环境方面具有明显效果。本文以安徽省合肥市主城区的18个城市公园为例,基于Landsat8OLI/TIRS遥感数据通过单窗算法反演出地温数据,采用缓冲区分析法计算城市公园的降温效应特征,从降温幅度和降温距离2个维度量化合肥市城市公园的冷岛效应,并分析公园中影响降温效应的主要因素,以期为城市热环境优化与绿地规划提供参考。

城市公园冷岛效应及影响因子分析——以昆明市三环内城市公园为例

随着城市热岛效应的不断加剧,提高城市公园冷岛效应有利于改善城市生态环境质量,建设宜居城市。文章以昆明市三环内城市公园为例,研究城市公园冷岛效应及其影响因子,基于Landsat 8遥感影像数据,对研究区40个城市公园样本景观格局与冷岛效应指标进行分析,结果如下:(1)研究区城市公园冷岛效应明显,最大降温距离(MCD)252.26m,最大降温幅度(MCM)0.18℃,最大降温梯度(MCG)0.00071℃/m;(2)昆明市城市公园面积阈值为1.101~10hm^(2);(3)不透水面占比小于70%具有较好的冷岛效应,有水体城市公园绿地面积应大于0.01 hm^(2),无水体城市公园绿地面积应大于0.03 hm^(2),水体面积应大于0.05 hm^(2),具有较好的降温效果。所得结论对城市公园设计具有一定指导意义,为城市公园大冷岛效应研究提供理论基础。

非均匀下垫面边界层的观测和数值模拟研究 (I):冷岛效应和逆湿现象的完整物理图像

利用HEIFE、DHEX和GAME/Tibet3个观测试验和部分常规气象站观测资料,分析了下垫面非均匀条件下产生的冷岛效应和逆湿现象的完整物理图像以及它们对地表能量和五水转化的影响。分析结果表明,下垫面非均匀特征对五水转化有着明显的影响;冷岛效应和逆湿现象是下垫面非均匀性的必然结果,它们在自然界普遍存在;现有陆面过程模式很难刻画冷岛效应和逆湿现象,通常现有陆面过程模式很难将冷岛效应中的热量平流转化成蒸发潜热,同时陆面过程模式也混淆了逆湿现象和发生在下垫面上的大气水的冷却凝结。这些评述将有助于今后非均匀陆面过程的进一步研究。

夏季金塔绿洲冷岛效应的数值模拟

利用中尺度数值模式MM5对金塔绿洲2003年7月31日～8月2日的观测资料进行了模拟研究,分析了金塔绿洲的温、湿、气压、风场演变.结果表明,绿洲上白天为湿冷中心,气压场表现为低层(850 hPa)高压,高层(700 hPa)低压.受背景场影响,温、湿、气压中心偏离绿洲中心,风场向背景风的垂直向辐散.但绿洲上的感热和潜热场形状不受背景风场影响,不产生变形、偏离,同绿洲形状重合.

区域尺度绿洲稳定性评价

论文在区域尺度上,探讨了绿洲稳定性的内涵,并以新疆三工河流域绿洲为例,从绿洲所处的地理位置、绿洲与外围荒漠和山地系统之间的相互作用等方面评价了绿洲的区域稳定性。结果表明:①冲洪积扇型绿洲稳定性最高,其次是位于地下水溢出带下方的冲积平原型绿洲,稳定性最差的是湖滨三角洲或散流干三角洲上发育的绿洲;②绿洲的冷岛效应和植被指数可较好地表征绿洲与外围荒漠和山地系统之间的相互作用和评价绿洲的区域稳定性的时间变化。绿洲规模的扩大及绿洲水分和植被的增加将加强绿洲的冷岛效应,提高绿洲的稳定性;归一化差异植被指数增加,表明绿洲内植被覆盖密度增大和植物生物量提高,绿洲的稳定性增强。

WRF模式对金塔绿洲效应的数值模拟

利用美国NCAR中心的天气研究与预报模式WRF,对金塔绿洲的温度场、环流场、能量场的结构及其日变化特征进行了较为细致的模拟研究。结果表明,WRF模式能较好地模拟出非均匀下垫面上绿洲和戈壁的近地面温度、风场、净辐射、感热和潜热等要素的变化特征及日变化规律,较为完整地呈现出绿洲"冷岛效应",模拟的近地面风向和观测值吻合较好。通过对能量场的时空分析,发现下垫面的植被类型、土壤类型和土壤湿度对绿洲白天感热、潜热、土壤热通量和净辐射等有很大影响,绿洲白天净辐射峰值比戈壁大,潜热通量比感热通量大;白天大气向地面传输热量,绿洲地表获得的热通量大;而夜间地表向上传递热量,绿洲释放的热通量比戈壁大。更加细致地研究这些现象对深入了解绿洲气候的形成和维持机理具有重要的意义。

夏季绿洲气候效应的观测和数值模拟

利用“金塔绿洲能量水分循环观测试验”的资料和中尺度数值模式对绿洲小气候效应进行了17天较长序列的研究，在模拟过程中每天替换土壤湿度。研究结果表明：在分析时段内2004年7月6目前和9日后分别盛行西北风和东风两种背景风；白天，绿洲低层相对沙漠是一个冷源，随着高度的增加逐渐转为暖中心，温度场在600～700hPa之间转变。当背景风较大时，绿洲上空的温度中心会偏向绿洲中心下游。白天绿洲低层风场平均态为在东风背景场的基础上向南北两侧辐散，随着高度的增加风场逐渐由辐散转为向绿洲的辐合，转变高度在700hPa以下，且低于温度场的转变高度。白天绿洲上以下沉运动为主，绿洲风次级环流是绿洲上夏季晴天长期存在的平均态。当背景风较小时绿洲低层可形成向四周辐散的风场，当背景风场过大时，无绿洲环流生成。绿洲为高湿场，在绿洲边缘沙漠上存在的逆湿和高水汽柱，既阻止沙漠上干热气流侵入绿洲，又防止绿洲上水汽的流失。白天沙漠、绿洲的地表能量通量差异较大，绿洲上以潜热为主，沙漠上以感热为主，二者量级相当。绿洲上的边界层高度低于沙漠的，对绿洲生态系统起一定的保护作用。

鄱阳湖地区大气边界层特征的数值模拟

采用WRFV2.2中尺度数值模式对鄱阳湖地区200 km×200 km范围内,2009年11月5日00:00至2009年11月6日12:00不同高度的气象要素进行了数值模拟,得到了水平分辨率为1km的鄱阳湖地区大气边界层风、温、湿度场和廓线分布的大气边界层物理特征.模拟结果发现:(1)白天鄱阳湖面上空存在着冷岛效应并伴随湖风,而夜间湖面上空存在着热岛效应并伴随陆风,湖面与陆地之间最大温差可达6℃;(2)地形以及下垫面类型对鄱阳湖区风场的分布具有很大影响,夜间存在一条东北西南走向的低空辐合带,白天逐渐消失;(3)受风场和地形作用湖面上空的湿度分布也不均匀,白天湿度层厚度低而夜晚湿度层厚度高,湖中心右侧湿度值大于左侧湿度值.模拟结果能较好地反映鄱阳湖的大气边界层物理特征,有助于了解鄱阳湖地区区域气候的特点,以及由于地形、地理环境、地表特征所形成的不同高度上的风、温、湿的分布规律和大气边界层物理特征,为鄱阳湖地区局地天气预报、风能资源开发、环境保护等提供了科学依据.